Valves designed for use with magnetorheological fluids are known in the art. As a fluid flows through such valves a magnetic field is applied to the magnetorheological fluid. The interaction between the ferromagnetic particles in the magnetorheological fluid increases the effective viscosity of the magnetorheological fluid in the valve. This change in viscosity causes the resistance to the fluid flowing through the valve to increase, and causes a proportional change in the inlet pressure to the valve, thereby slowing or stopping the fluid flow.
Known magnetorheological valves are generally large and consume a large amount of power due to the large volume occupied by the hydraulic line. Known magnetorheological valves also have a high initial hydraulic resistance, which limits those valves to a narrow control range. The response speed of these devices is generally slow.
Germer, U.S. Pat. No. 2,670,749, describes a valve for controlling the flow of fluids by means of a magnetic oil. Germer discloses a method of controlling the flow of a fluid by passing the fluid through a magnetic oil subjected to a magnetic field. When the magnetic oil becomes magnetized, it thickens to a semi-solid state and offers increased resistance to a flow of fluids passing through it.
A means for controlling the flow of a traditional fluid is also shown in Japanese Patent No. 63-83476. In the 63-83476 patent, a magnetic fluid positioned within a magnetic inductor is used to drive an intermediate element to control the flow of fluid through the valve.
Neither Germer nor Japanese Patent No. 63-83476 teaches a means for controlling the flow of the magnetic fluid itself. In addition, in valves such as those described in Germer and 63-83476, improvements in response time, power consumption, and overall dimensions are limited by the capacity of the magnetic field to magnetize the magnetic fluid.